import java.util.HashSet;
import java.util.List;
import java.util.Set;

class Solution {
    public boolean wordBreak(String s, List<String> wordDict) {
        Set<String> set = new HashSet<>(wordDict);
        int n = s.length();
        boolean[] dp = new boolean[n+1];
        dp[0] = true;
        s = " " + s;
        for(int i = 0; i <= n; i++) {
            for(int j = i; j > 0; j--) {
                if(dp[j-1] && set.contains(s.substring(j, i + 1))) {
                    dp[i] = true;
                    break;
                }
            }
        }
        return dp[n];
    }
}